KPNO-Tau 12 was identified in 2003 in data from a survey of theTaurus Molecular Clouds taken with a telescope at theKitt Peak National Observatory (KPNO) and2MASS. The object was observed with theMMT Observatory/Blue Channel spectrometer and withKeck/LRIS. KPNO-Tau 12 showed a spectral type of M9 and also showed strongHydrogen-alpha emission. At the time its mass was estimated to be around 0.02M☉ (or 21MJ), which would make it a brown dwarf.[8] Since then several works found that it likely has a mass near or below thedeuterium-burning limit, which makes this object a low-mass brown dwarf or planetary-mass object (e.g. 14.6MJ,[3] 13.6MJ,[9] 6-7MJ,[4] 16.5MJ,[10]17.8+6.7 −4.6MJ,[11]12.7+1.6 −1.8MJ[6]).
A few other free-floating planetary-mass objects are known in the Taurus Clouds.[12][13] These include three other objects with possible disks around them.[13]
Observations with Keck/LRIS showed several absorption features. These aretitanium oxide,calcium hydride,vanadium oxide,sodium andpotassium.[8] A spectrum with Keck/NIRSPEC was interpreted to be consistent with very lowgravity. This is typical for young sources.[14] Several re-classifications of the spectral type were made over the years. In 2013 it was re-classified as a M9.25±0.5.[4] In 2018 it was re-classified as a L0.7±1.1, which could make this object an earlyL-dwarf.[5] A spectrum observed withVLT/SINFONI was published in 2022, estimating a spectral type of M9.8.[15]
KPNO-Tau 12 showed strongest H-alpha emission in both the MMT and Keck optical spectra. It also showedhelium (He I) andcalcium (Ca II IR triplet) emission in the Keck spectrum, which are usually seen in stars that undergo intenseaccretion of material from a surroundingprotoplanetary disk.[8] Additionally a Keck infrared spectrum shows a prominent emission line (see figure 10 of their work), which is described asPaschen β at 1.28 μm in the appendix of the paper.[14] Paschen lines can be used as additional accretion indicators.[16] In 2010 two works used observations with theSpitzer Space Telescope. These two works first identifiedinfrared excess around KPNO-Tau 12 and classified it as a class II disk. A class II disk is composed of both a gaseous and a dusty part and belongs to the protoplanetary disks.[17][18] Observation with the Spitzer Infrared Spectrograph showed that thesilicate emission feature is likely missing.[19] The dust mass of the disk was estimated to be1.223M🜨[10] or0.6–1.1M🜨,[20] depending on the work. The total (gas+dust) mass was estimated to be0.66MJ[11] or0.095MJ,[21] depending on the work. The dust temperature was estimated to be7.0±13.8Kelvin and the dust grains are smaller than 27.5millimeters.[20]
^Rebull, L. M.; Padgett, D. L.; McCabe, C.-E.; Hillenbrand, L. A.; Stapelfeldt, K. R.; Noriega-Crespo, A.; Carey, S. J.; Brooke, T.; Huard, T.; Terebey, S.; Audard, M.; Monin, J.-L.; Fukagawa, M.; Güdel, M.; Knapp, G. R. (February 2010). "The Taurus Spitzer Survey: New Candidate Taurus Members Selected Using Sensitive Mid-Infrared Photometry".The Astrophysical Journal Supplement Series.186 (2):259–307.arXiv:0911.3176.Bibcode:2010ApJS..186..259R.doi:10.1088/0067-0049/186/2/259.ISSN0067-0049.
^Furlan, E.; Luhman, K. L.; Espaillat, C.; D'Alessio, P.; Adame, L.; Manoj, P.; Kim, K. H.; Watson, Dan M.; Forrest, W. J.; McClure, M. K.; Calvet, N.; Sargent, B. A.; Green, J. D.; Fischer, W. J. (July 2011). "The Spitzer Infrared Spectrograph Survey of T Tauri Stars in Taurus".The Astrophysical Journal Supplement Series.195 (1): 3.Bibcode:2011ApJS..195....3F.doi:10.1088/0067-0049/195/1/3.ISSN0067-0049.
